(a) Field of the Invention
The present invention relates to a secondary battery, and in particular, to an anode tab for a negative plate of an electrode group.
(b) Description of Related Art
Generally, batteries are largely classified into a secondary battery which can be repeatedly charged and discharged, and a primary battery which is not rechargeable, and is disposed of after it becomes depleted. Batteries are formed with various shapes, such as a cylindrical shape, a prismatic shape, and a pouch shape, depending upon the profile of the target appliances.
Among them, the cylindrical-shaped secondary battery has an electrode assembly where a negative plate and a positive plate are rolled in the form of a jelly-roll while interposing a separator therebetween, a cylindrical can mounting the electrode assembly therein, and a cap assembly fitted to the top of the can.
An insulating plate is disposed between the electrode assembly and the cap assembly as well as between the electrode assembly and the can.
The positive plate of the electrode assembly is electrically connected to the cap assembly via a cathode tab, and the negative plate of the electrode assembly is electrically connected to the can via an anode tab.
The anode tab is mainly formed with a nickel strip having a thickness of 0.05-0.1 mm, and it is welded to the negative plate located at the outermost area of the electrode assembly and the inner bottom surface of the can to electrically interconnect the negative plate and the can.
However, as the nickel strip used as the anode tab is rigid, when the electrode assembly welded with the anode tab is inserted into the can, the anode tab is liable to be stuck at the opening portion of the can, thereby incurring an abnormality in the arrangement of the electrode assembly
In this connection, the outer diameter of the electrode assembly is designed such that when the electrode assembly is inserted into the can, a margin (for instance, of 0.2-0.4 mm) is allowed between them. However, this makes the electrode assembly limited in its dimensions, and hence, the electrode assembly cannot be enlarged within the can enough to heighten the battery capacity.